1. The Technical Field
The present invention relates to touch switches. More particularly, it relates to the integration of touch switches into control panels and other substrates using molding techniques such as thermoforming, injection molding, and the like.
2. The Prior Art
Touch switches have many advantages over and have long been used as replacements for mechanical switches. Known touch switches typically include a touch pad and an associated control circuit. Such a touch pad typically consists of one or more electrodes and, in some cases, other electronic components, mounted on a rigid or flexible carrier. The associated control circuit can be mounted on the carrier proximate the touch pad or distant from the touch pad, or elsewhere. The touch switch carrier typically is attached to another pre-formed panel having one or more touch surfaces corresponding to the touch pads on the touch switch carrier. This panel, or touch surface substrate (also referred to herein as a control panel and/or control panel substrate), typically is made of glass or plastic and can include structure and features that provide an ergonomic or decorative control panel interface. The touch switch carrier typically is attached to the touch surface substrate using mechanical means such as stud and bracket structures, snap-in plastic assemblies, adhesives or a combination of these and other mechanical attachment structures and techniques.
A user typically actuates such a touch switch by touching or approaching with an appendage or other object a corresponding touch surface on the touch surface substrate, thus causing a response in the touch switch's associated control circuit. This response can be affected by factors such as separation (distance) between the touch pad and the touch surface and material properties of the panels comprising the touch switch carrier and the touch surface substrate, among others. Further details regarding the design and operation of touch switches can be found in, for example, U.S. Pat. Nos. 5,594,222, 5,856,646, 6,310,611 and 6,320,282 B1.
While the foregoing conventional assembly techniques generally are effective, they sometimes provide less than optimal integration of the touch switch carrier to the touch surface substrate, thus potentially adversely affecting the operation of the touch switch. For instance, stud and bracket attachment methods sometimes yield inconsistent spacing between touch pads and the corresponding touch surfaces on the touch surface substrate because of mechanical irregularities in the attachment components, the touch switch carrier, and/or the touch surface substrate. Also, stud and bracket assemblies can come apart, particularly in vibratory or other harsh environments. Simple adhesive attachment methods can yield inconsistent spacing between touch switches and corresponding touch surfaces in cases where adhesive is unevenly applied between the touch switch carrier and the touch surface substrate. Also, bubbles and other inconsistencies in the composition of the adhesive itself can adversely affect the performance of the touch switch.
Further, the foregoing conventional techniques impose limitations on the design of the final touch switch/touch surface interface. For instance, the pre-formed substrates to which touch switches are conventionally attached typically are flat to facilitate the fabrication and attachment processes. Attaching a touch switch to a non-flat substrate using conventional attachment techniques can pose problems related to the complexity of the attachment process and the surety of the attachment itself.